Star Trek: 10 Starfleet Officers Who Betrayed The Federation
3. Captain Benjamin Sisko
The truth is, there are a few times that Sisko could have ended up on this list. Initially, he fails to inform Starfleet of Calvin Hudon's betrayal. Then, he takes the Defiant into the Gamma Quadrant to save Odo and Garak, disobeying a direct order to do so.
Later, he uses the Defiant's cloaking device while in the Alpha Quadrant (technically a betrayal of the agreement with the Romulans, though this is an agreement between Starfleet and the Empire.)
There is also an argument for including his actions that led to the Romulans joining the war. Though the plan was sanctioned by Starfleet, it most certainly is a betrayal of the principals of the Federation.
However, the entry here revolves around his hunt for Michael Eddington. He allowed the search for the former security officer to become deeply personal, resulting in man hours and resources being diverted to finding him. This resulted in Starfleet taking him off the search, reassigning it to the USS Malinche - which was later attacked and disabled by Eddington.
Against orders, Sisko takes the Defiant back out to hunt. However, he heads for a Maquis colony and issues a general warning that he is about to detonate trilithium resin into the atmosphere, rendering the planet uninhabitable. Though Eddington attempts to call his bluff, Sisko orders a visibly disturbed Worf to fire.
Eddington does surrender, but he calls it: Sisko betrayed his oath to Starfleet, just to hunt down the man who beat him. Sisko technically won the day, but it came at a heavy cost.